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问题 实验题

如图所示，某同学做测定滑轮组的机械效率实验时，第一次用图甲的装置，第二次用图乙的装置，若每个滑轮的重力都相等，两次实验中所提升的重物G是同样的钩码，则

（1）装置图_______所示的滑轮组更省力；

（2）装置图_______所示的滑轮组的机械效率高，这是因为_____________________；

（3）如果两次实验中所提钩码G的重力都是4N，钩码匀速上升时，弹簧秤的示数分别是F甲=1.5 N，F乙=1.2 N，那么这两个滑轮组的机械效率分别是η甲=_______，η乙=_______。

答案

（1）乙

（2）甲；甲滑轮组中动滑轮的重力小，做的额外功少

（3）88.9%；66.7%

解答题
已知函数f（x）=
3
sinxcosx-sin2x+
1
2
，x∈R，
（I）求函数f（x）的最小正周期、最大值及取得最大值时自变量x的集合；
（Ⅱ）设g（x）=f（x+
π
6
），试判断函数g（x）的奇偶性．
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单项选择题

Industrial pollution is not only a problem for the countries of Europe and North America but also an extremely serious problem in some developing countries. For these countries, economic growth is a very important aim. They want to introduce industries, and so they put few controls on the industries which cause pollution.
Cubatao, an industrial town of 85 000 people in Brazil, is an example of the connection between industrial development and pollution. In 1954, Cubatao had no industry. Today it has more than twenty large factories, which produce many pollutants. The people of the town are suffering from the poisonous matter in their environment and the bad effects can be clearly seen. Birth shortcomings are extremely common. Among children and adults, lung problems are sometimes twelve times more common in Cubatao than in other places.
It is true that Brazil, like many other countries, has laws against pollution, but these laws are not enforced strictly enough. It is cheaper for companies to take no notice of the laws and pay the fines than to buy the expensive equipment that will reduce the pollution. It is clear, therefore, that economic growth is more important to the government than to the health of the workers. However, the responsibility does not completely lie with the Brazilian government. The example of Cubatao shows that international companies are not acting in a responsible way either. A number of the factories in the town are owned by large companies from France, Italy, and the US. They are doing things in Brazil that they would not be able to do at home. If they caused the same amount of pollution at home, they would be severely punished or even put out of business.

What is the author’s purpose in taking Cubatao as an example

A. To show that industry can develop very fast in developing countries.
B. To show that the pollution problem in Brazil is extremely serious.
C. To show that industrial growth can cause pollution problems for developing countries.
D. To show that pollution is killing many people and destroying the whole economy of Brazil.
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